Patent Application
20130146473
The present invention relates to a cylindrical electrolysis cell assembly for producing simultaneously a diluted Sodium Hydroxide and diluted Hypochlorous Acid solution for usage as cleaning and sanitizing solutions by electrolysis of an aqueous saline solution. The method comprising a cathode chamber, an electrolyte chamber and an anode chamber separated by two cylindrical diaphragms to prevent presence of salt residues in the cleaning and sanitizing solutions and whereas pH and free available chlorine content of the sanitizing solution can be altered.
Electrolysis cells are used for the production of cleaning and sanitizing solutions from brine. Also, electrolysis cells are used to produce a sanitizing solution to disinfect water or other media. Many types of electrolysis cells exist for these purposes. The basic feature of these cells is two concentrically disposed cylindrical electrodes with a diaphragm separating the space between the two electrodes to define anode and cathode compartments. An electrolyte, such as brine, is passed through the anode and cathode compartments, separately or successively. When brine is electrolyzed in this way, under suitable conditions, it can produce a cleaning and sanitizing solution of high strength and long shelf life, which is ecologically and human friendly.
Typically an electrolyte solution is passed through the anode and cathode chambers separately to produce a diluted Hypochlorous Acid solution as a sanitizing solution and a diluted Sodium Hydroxide solution as a cleaning solution. Alternatively, neutral sanitizing solutions can be produced when an electrolyte is passed through the anode and cathode chambers successively.
The diaphragm is either made of a permeable ceramic or an ion-exchange membrane. The diaphragm permits the diffusion of electrolytes between the anode and cathode but retard the migration of electrolysis products at the anode and cathode from diffusing to each other reverting back to starting material or undesired side products.
Acidic sanitizing solutions are generated by passing saline through an electrolytic cell comprising an anode chamber, a cathode chamber, and a separator. The result contains free available chlorine (FAC) in the form of a mixture of oxidizing species, predominantly Hypochlorous Acid (HOCl) and sodium hypochlorite, and is characterized by its pH, FAC content, and redox level. Such reactive species have a finite life and so, while the pH of the solution will usually stay constant over time, its biocide efficacy will decrease with age. Electrolysis cells either comprise cylindrical electrodes plus one cylindrical ceramic diaphragm or electrolysis cells comprise plate electrodes plus one ion permeable sheet of membrane as separator.
Usage of insoluble ion permeable membranes or ceramic diaphragms between the electrodes have been described for more than 100 years as, for example, that described in U.S. Pat. No. 590,826. U.S. Pat. No. 914,856 describes a cell which permits the flow of electrolyte solutions separately through the anode and cathode compartments using concentric cylindrical electrodes with an ion permeable diaphragm.
The three-chamber cell has the following merits. Reductive species such as dissolved hydrogen gas produced in the cathode chamber are likely to migrate into the anode chamber through the diaphragm when utilizing a two chamber cell, such as described in U.S. Pat. No. 7,374,645, U.S. Pat. No. 7,691,249 or in U.S. Pat. No. 7,828,942. However, the middle chamber in the three-chamber cell control the diffusion of reductive species from the cathode chamber to the anode chamber and then the more strongly oxidative anode water can be obtained.
In the cell shown in
2H2O→2H++O2+2e− [1]
2H++2e−→H2 [2]
These reactions increase the oxygen concentration in the anode solution and the hydrogen concentration in the cathode solution, while leaving the essential properties of electrolytic water unchanged. Further, migration of hydrogen ions formed on the anode toward the cathode is limited, and then the electrolysis reaction [3] takes place in addition to the reaction [1] and [2]:
H2O+2e−→½H2+OH− [3]
This reaction suggests that the pH of cathode water tends to shift to the alkaline region. Hydrogen ions formed in the anode chamber in the reaction [1] remain partly in that chamber. In the two-chamber cell shown in
In order to enhance the cleaning or surface treatment efficacy, anode water is required to be more oxidative and/or acidic and cathode water is required to be more reductive and/or alkaline. However, the electrolysis cell shown in
The three-chamber cell shown in
Another merit of a three chamber cell is the fact that no electrolyte is fed into the anode and cathode chamber. Although efficiency of two chamber electrolysis cells has been significantly improved, not all electrolytes that pass the cathode chamber are conversed into Sodium Hydroxide. Likewise, not all electrolytes that pass the anode chamber are conversed into Hypochlorous Acid and/or Hypochlorite Ion.
As a result, both the cleaning and sanitizing solutions generated in a two cell electrolysis cell contain salt residues. Presence of salt in both the cleaning and sanitizing solutions limit its usage for surface treatment, as salt is corrosive, streaks the surface, and leaves deposits on the surface. As a result, most cleaning and sanitizing procedures include an extra rinse with potable water.
This invention resolves the deposits of salt and thus allows for cleaning and sanitation of surfaces without additional rinsing.
The invention is directed to a cylindrical dual diaphragm electrolysis cell assembly comprising a cathode chamber, electrolyte chamber, and an anode chamber. The present invention provides an insulating end piece for a cylindrical electrolysis cell of the type comprising at least two cylindrical electrodes arranged coaxially one within the other with two cylindrical diaphragms arranged coaxially between them.
Softened filtered water passed through the cathode chamber functions as cleaning agent for all surfaces, fabrics, textiles, and carpets. Softened filtered water passed through the anode chamber functions as sanitizing agent for all hard surfaces.
Anodic electrolysis of softened water produces hydrogen ions, where no anion is present as counter ion, unlike acidic solutions prepared by adding acid such as hydrochloric acid or sulfuric acid. The anode water produced by electrolyzing softened water exhibits that the solution is charged. Moreover, the hydrogen ion by itself is an electron acceptor and so exhibits one of oxidizing species. So, the oxidation-reduction potential of anode water tends to shift to noble side. In other words, the redox sensor indicates a plus value. During cathodic electrolysis of softened water is reduced at the cathode. This occurs because water is more easily reduced than are sodium ions. Cathodic electrolysis alters the H+/OH− balance around the cathode making the solution more basic and the oxidation reduction potential of cathode becomes negative.
When the two-chamber cell depicted in
More specifically, the important factors for producing effective cleaning and sanitizing agents are an apparent current density (current (A)/apparent area of whole electrode (cm.sup.2), a fluid velocity along the electrode surface, and a true current density (effective current density=current (A)/true area of the electrode (cm.sup.2)). As the fluid velocity increases, the hydrogen ions and other electrolytic species produced on the electrode surface migrate faster.
Various different sanitizing solutions can be produced in the electrolysis cells of the present invention, depending on the various flow patterns through the cell. For example, the softened water can be fed to the anode and cathode chambers and the electrolyzed solutions can then be collected from each of these chambers separately. Alternatively, the softened water can be fed through both the cathode and anode chambers successively. Other factors which can be used to vary the sanitizing solution include the voltage applied to the electrodes, the electrical power absorbed, the electrode coating and physical size of the electrode, the shape of the electrodes and distances between them and the spacing and material of the membrane. The membrane material is also an important feature since it affects the mobility of ions passing between the electrodes.
An objective of the invention is to provide a cylindrical electrolytic cell than can produce diluted Sodium Hydroxide and simultaneously diluted Hypochlorous Acid whereas the pH and the free chlorine content can be adjusted.
Another objective of the invention is to disclose a method and apparatus that can prevent the presence of salt residues in cleaning and sanitizing solutions whereas pH and free available chlorine content of the sanitizing solution can be altered.
Another objective of the invention is to improve cleanliness, as the cleaning solutions produced by the electrolytic cell are effective for cleaning all surfaces by removing fine particles or the like wherefrom and sanitizing solutions produced by the electrolytic cell are effective for sanitizing all hard surfaces by oxidation of micro-organism and viruses.
Yet another objective of the invention is to produce cleaning and sanitizing solutions that are also effective for cleaning and sanitizing resins or the like, in particular resins for beverage, dairy, and even medical devices.
Yet still another objective of the invention is to produce cleaning and sanitizing solutions wherein no special chemical remains after cleaning and sanitizing.
Other objectives and further advantages and benefits associated with this invention will be apparent to those skilled in the art from the description, examples and claims which follow.
The present invention is directed to the construction of an optimized cylindrical electrolysis cell that produces a cleaning solution and simultaneously a sanitizing solution. The diluted Sodium Hydroxide solution is more alkaline, contains no salt residues and, therefore, the solutions can be used to clean any surface without rinsing the surface afterwards with distilled, RO water or tap water. The diluted Hypochlorous Acid solution contains no salt residues and its free available chlorine content as well as pH can be adjusted. As a result, surfaces can be effectively sanitized using a sanitizing solution which pH and free available chlorine is ‘tailored’ to sanitize a certain surface taking into account chlorine consumption and in line with various sanitizing procedures as set by regulatory agencies such as the FDA, EPA, USDA and CDC. Certain surfaces require a more acidic sanitizer whereas other surfaces are damaged by the acid nature of the sanitizer. In these cases, a more neutral pH Hypochlorous Acid is preferred. Also, the absence of salt residues allows the use of the sanitizing solution on any surface without rinsing the surface with distilled, RO or tap water.
The three chamber electrolysis cell is illustrated in
The design of the four sections of the end piece [99] permits the orientation and sealing of the entire assembly [100]. Tube cap [6] seals the outer electrode [4] with the end piece [99] using an O-ring [12]. The tube cap [6] is either glued or screwed on the outer electrode [4]. In case the tube cap [6] is screwed on the outer electrode [4], the outer electrode tube-ends have a male thread that fits a female thread manufactured in the tube cap [6].
Port A cap [7] features port A for direction of the flow of softened water through port A ending in fittings [17] into the chamber A defined by the spaces between the anode [4] and the diaphragm [3] and out of chamber A through port A ending in fittings [17] of the opposite port A cap [6].
Port B cap [8] features port B for direction of the flow of saturated brine through port B ending in fittings [17] into chamber B defined by the spaces between the diaphragm [2] and diaphragm [3] and out of chamber B through port B ending in fittings [17] of the opposite port B cap [8].
Port C cap [9] features port C for direction of the flow of softened water through port C ending in fittings [17] into chamber C defined by the spaces between the inner electrode [1] and the diaphragm [2] and out of chamber C through port C ending in fittings [17] of the opposite port C cap [9].
The four sections of end piece [99] are either glued on each other or compressed on each other using O-rings [13] to seal the section on each other.
The tube cap [6] is either glued or screwed on the outer electrode [4]. Port A cap [7] is either glued or pressed on the tube cap [6] whereas the tube cap [6] facilitated a groove for an O-ring [13] and whereas port A cap [7] is pressed on the tube cap [6]. Port B cap [8] is either glued or pressed on port A cap [7] whereas the port A cap [7] facilitated a groove for an O-ring [13] and whereas the Port B cap [8] is pressed on port A cap [7]. Port C cap [8] is either glued or pressed on port B cap [7] whereas port B cap [7] facilitated a groove for an O-ring [13] and whereas port C cap [8] is pressed on port B cap [7].
The tube cap [6], port A cap [7], port B cap [8] and port C cap [8] are bolted together using three stainless steel bolts [18], washers [19] and nuts [20]. In each section of the end piece [99], there are three holes [21] to facilitate the stainless steel bolts [18], washers [19] and nuts [20]. The seal between each section of the end piece [99] is achieved by compressing the sections of the end piece [99] onto each other, in a manner such that the compressive force can be applied slowly and smoothly without the introduction of torque such that a reliable seal is produced without damaging the ceramic diaphragms [2] and [3].
Either of the electrodes [1] and [4] can act as the anode with the other acting as the cathode. The choice can be made by considerations of the ease of manufacture or requirements of the nature of the electrolysis process to be performed which can favor the anode or cathode chamber preferentially being the outer chamber. These considerations include the desired spacing between the electrodes and the diaphragms, the desired space between diaphragm [2] and [3] and the relative volume requirements for the balance of flows of the electrolyte solution in chamber B and the softened water in chamber A and chamber C.
The inner electrode [1] and outer electrode [4] tubes are constructed of an electrically conductive material, preferably titanium.
The metal electrode tubes are coated with a mixed metal oxide on the face of the tube directed toward the diaphragms [2] and [3]. The metals of the two electrodes can be titanium or stainless steel. Both metals can be coated with a mixed metal oxide. The cathode can be an uncoated metal, but the anode has to be a mixed metal oxide coated metal. A preferred arrangement has the outside electrode tube [4] as the anode internally coated with a mixed metal oxide and the inner electrode tube [1] as the cathode and not coated.
The outer electrode [4] is shown in
The anode and cathode are separated by two diaphragms [2] and [3]. Preferably, these diaphragms are made of alumina, zirconium containing ceramic. The thickness of the diaphragm can vary over a broad range depending on the application the electrolysis cell assembly [100] is to be used, the diaphragms [2] and [3] are relatively fragile and a wall thickness of 1.5 to 2 mm is preferred for most applications.
The relative diameter of the outer electrode [4], inner electrode [1], diaphragms [2] and [3] can vary within the single requirement that outer electrode [4] must be of greater diameter than diaphragm [3], the diameter of diaphragm [3] greater than diaphragm [2] and the diameter of diaphragm [3] greater than the inner electrode tube [4]. The actual diameters can vary depending upon the desired features of the electrolysis cell assembly [100]. To this end the diameters can be varied to optimize the rate of electrolysis, rate of flow through the cell assembly, and other needs of the system to which the assembly will be used. Likewise, the relative length of the electrodes [1] and [4] and diaphragms [2] and [3] can vary within the single requirement of this embodiment that the outer electrode tube [4] must be shorter than diaphragm [3], diaphragm [3] shorter than diaphragm [2] and diaphragm [2] shorter than inner electrode [1]. The lengths of the electrodes [1] and [4] and the length of the diaphragms [2] and [3] can be determined by factors such as ease of construction and geometries to optimize the performance of the electrolysis cell assembly in the system in which it is to perform.
The upper and lower end pieces [99] are interchangeable and constructed of an insulating material, preferably Polyvinyl Chloride. Each end piece [99] consist of four sections, the tube cap [6], Port A cap [7], Port B cap [8] and port C cap [9].
The four sections of the end piece [99] can be formed by molding or machining. Ports [17] are for introduction or exit of softened water to chamber A and to chamber C. Port [17] is for the introduction and exit of electrolyte to chamber B. All sections of the end piece [99] consist of three or more holes to accept three or more stainless steel bolts [18], washers [19] and nuts [20] by which the four sections of the end piece [99] are compressed together.
Three sections [6], [7] and [9] of the end piece [99] have a groove to facilitate O-ring [13] to form the seals between the end piece sections. When the tube cap [6] is screwed on the outer electrode [4] and stainless steel bolts [18], washers [19] and nuts [20] are used, then the three bolts provide the structural integrity of the assembly [100]. If the tube cap [6] is glued on the outer electrode [4], then the three sections of the end piece [99] are also glued together.
Two holes [22] with female thread are made in the tube cap [6] at both opposite sides. This allows mounting the assembly [100] on a plate or bracket. This plate or bracket may be a plastic or stainless steel as long as the metal is insulated from one or both of the electrodes. A preferred fabrication of a mounting plate or bracket is a machined sheet of Polyvinyl Chloride, which is commercially available as PVC.
One critical feature of the end piece [99] is that the inside diameter of all sections of the end piece [99] closely match the outside diameters of the four tubes [1], [2], [3] and [4] so that when using glue as a sealant, a good seal can be achieved. When screwing the tube cap [6] on the outer electrode [4] and when the other sections of the end piece [99] are compressed on each other, it is important that the O-rings [12], [14], [15] and [16] form a good seal between the tubes [1], [2], [3] and [4] and the four end caps [6], [7], [8] and [9] as well form a good seal between the four sections themselves using O-ring [13]. The relatively fragile diaphragms [2] and [3] require the use of O-rings [14] and [15] to form the seal such that whilst assembling, the diaphragms do not break. It is necessary that, upon assembly, the length of the cell assembly [100] is defined by the length imposed by the outer electrode tube [4]. The diaphragms [2] and [3] must be long enough to seal at both ends by O-rings [14] and [15] even if one end of the diaphragms [2] and [3] is resting on Port B cap [8] and Port C cap [9].
A second critical feature of the end caps [99] is the presence of three ports. Port A begins at fitting [17] on an outside surface of Port A [7] permits the flow of softened water through chamber A defined by the inside of the outer electrode tube [4] and the outside of diaphragm [3] as illustrated in
These fittings [17] can be a compression fitting, as is illustrated in
The end pieces [99] can have other configurations as long as the configuration permits for the sealing of the assembly where the compressive force is imposed upon the outer electrode [4] and no significant compressive force is imposed on the diaphragms [2] and [3]. The different types of end pieces [99] can be combined in any combination as long as the appropriate lengths of tubing are chosen and as long as the sections of the end piece [99] can be sealed together by compression or by using glue. While the preferred end piece [99] has been illustrated and described, it will be clear that the invention is not so limited. Modifications, changes, variations, substitutions and equivalents will occur to those skilled in the art without departing from the spirit and scope of the present invention as described in the claims.
Another critical feature of this invention is the construction of the brine reservoir [98] and the usage of a pump [23] to circulate an electrolyte from the brine reservoir [98] through chamber B to the brine reservoir [98] as shown in
This three chamber cylindrical electrolysis cell can be used with different flow patterns allowing changing the volume of the cleaning and sanitizing solution, as well the pH and free available chlorine content. A typical flow pattern permits approximately 30 to 70% of the softened water to pass the anode chamber and approximately 70 to 30% of the softened water to pass the cathode chamber. The volume of softened water that passes the anode chamber or cathode chamber can be restricted by closing a valve which is mounted in the outlet tube of the anode chamber and the volume of softened water that passes the cathode chamber can be restricted by closing a valve that is mounted in the outlet tube of the cathode chamber. An alternative flow pattern is a flow pattern whereas 100% of the softened water is passed through either the cathode chamber or anode chamber. Approximately 70 to 100% of the electrolyzed solution that either exits the cathode chamber or anode chamber is re-directed to the inlet of either the anode chamber or the cathode chamber whereas 0 to 30% of the electrolyzed liquid is collected in a Sodium Hydroxide storage container or drained as useful by-product. This alternative flow pattern whereas 70 to 100% of the electrolyzed solution is collected in a Hypochlorous Acid storage container is preferred when there is no or little usage of the by-product and whereas the volume of the main-product is maximized. A preferred alternative flow pattern is to pass softened water first through the cathode chamber, wherein the outlet tube is a tee mounted to allow approximately 20% of the diluted sodium hydroxide to flow to a storage tank and where approximately 80% of the diluted sodium hydroxide is re-entered in the anode chamber. The result of this preferred alternative flow pattern is that approximately 80% of the softened water has undergone cathodic electrolysis followed by anodic electrolysis to generate a neutral pH sanitizing solution. Re-entering more diluted Sodium Hydroxide into the anode chamber will increase the pH of the diluted Hypochlorous Acid and re-entering less diluted Sodium Hydroxide will reduce the pH of the diluted Hypochlorous Acid. The volume of the diluted Sodium Hydroxide that enters the anode chamber is regulated by a valve that is mounted in the outlet tube of the cathode chamber between the tee and the Sodium Hydroxide storage container.
One skilled in the art will readily appreciate that the present invention is well adapted to carry out the objectives and obtain the ends and advantages mentioned, as well as those inherent therein. The embodiments, methods, procedures and techniques described herein are presently representative of the preferred embodiments, are intended to be exemplary and are not intended as limitations on the scope. Changes therein and other uses will occur to those skilled in the art which are encompassed within the spirit of the invention and are defined by the scope of the appended claims. Although the invention has been described in connection with specific preferred embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments. Indeed, various modifications of the described modes for carrying out the invention which are obvious to those skilled in the art are intended to be within the scope of the following claims.
